Automotive powertrains, which generally comprise an engine and transaxle, utilize roll restrictors to prevent unwanted rotation of the engine and transaxle about an axis which, if not coincidental with the engine's crankshaft center axis, is at least parallel thereto. Known automotive powertrain roll restrictors utilize brackets for attaching the restrictor to the transaxle or engine.
In this regard, FIG. 1 shows a roll restrictor system for an automotive powertrain 10 known in the prior art, which was previously disclosed in U.S. Pat. No. 8,215,444B2. The powertrain 10 has an engine 14 and a transaxle 18 with a longitudinal center line A. The powertrain 10 also includes a roll restriction system. The transaxle 18 includes a first mounting pad 22 to which a mounting bracket 26 is attached. A control link 42 connects bracket 26 to a vehicle structural member 46.
A powertrain roll restrictor has many functions. It must simultaneously isolate engine excitation forces at both idle (small force preloads) and wide open throttle (large force preloads), while also controlling powertrain roll during highly transient dynamic events. These conflicting requirements require a part that allows sufficient displacement with a low rate of change of stiffness.
In addition, it is desirable that within the package constraints, a roll restrictor is large enough to allow sufficient rubber volume to meet attribute and durability requirements, while also meeting metal strength and joint capacity criteria. It is also desirable that a roll restrictor allows ease of manufacture by the supplier and ease of assembly within the vehicle assembly plant. Finally, it is desirable that a roll restrictor meets service requirements in terms of replacement time without the need for special tooling or procedures.